1. Field of the Invention
The invention relates to a device and a method for reading an exposed imaging plate.
2. Description of Related Art
In X-ray technology, particularly in dental X-ray technology, imaging plates are used nowadays for the purpose of recording X-ray images. These imaging plates include a phosphor material which has been embedded in a transparent matrix. As a result, so-called storage centres arise, which can be brought into excited metastable states by incident X-ray light. If such an imaging plate is exposed in an X-ray apparatus, for example for the purpose of recording the dentition of a patient, the imaging plate contains a latent X-ray image in the form of excited and non-excited storage centres.
For the purpose of reading the imaging plates, the latter are scanned with read-out light, point by point, in a scanner, as a result of which the metastable states of the excited storage centres are brought into a state that relaxes rapidly, emitting fluorescent light. This fluorescent light can be registered with the aid of a detector unit, so that the X-ray image can be made visible with appropriate evaluating electronics.
Conventional scanners, such as a drum scanner for example, conduct the imaging plate along a cylindrical surface across a read-out gap. In the interior of the cylindrical surface a rotary mirror has been provided by way of deflection unit, which generates a circumferential read-out beam. The latter falls through the read-out gap onto the imaging plate and reads the latter in pointwise manner. Meanwhile the imaging plate is conducted past the read-out gap by a mechanical drive, so that the entire surface of the imaging plate is registered.
With such a drum scanner, particularly in the dental field in which mostly small-format imaging plates come into operation, it is disadvantageous that the imaging plate has been arranged only along a small region of the periphery of the cylinder. For a large proportion of the read-out time the read-out beam therefore circulates within a region where no imaging plate is present, so that, on average, the read-out beam actually impinges on the imaging plate only during approximately 10% of the read-out time. This results in unnecessarily long read-out times.